1. Field of the Invention
The invention relates to content-based filtering of multicast information.
2. Related Art
In a network of devices in which information is to be distributed to a large number of devices, it is known to transmit "multicast" messages, that is, messages which have multiple recipients and which are recognized by routers and routing protocols as intended to be delivered to multiple destinations. When information is to be delivered to a large number of recipients, it may be advantageous to use multicast techniques to deliver that information without incurring substantial additional overhead for administrative delivery requirements. Applications are known which use multicast techniques to deliver the same information to multiple recipients on a network, or on a network of networks such as an internet or an intranet. One known protocol, IGMP (Internet Group Management Protocol), uses a multicast address to distinguish between sets of recipients for multicast packets in an internet.
However, a problem has arisen in the art in the case when it is desired to deliver differing information to multiple recipients on a network. Because the information to be delivered is different for each recipient, or for each set of recipients in a specified interest group, there is a need to distinguish information by its content or subject matter, so that recipients which are interested in particular subjects can receive only that information of interest. However, when information is distinguished by content, the number of differing sets of information to be delivered can rapidly overwhelm any number of multicast addresses which can reasonably be reserved for differing sets of recipients.
Accordingly, it would be advantageous to provide a method and system for distributing potentially large numbers of categories of differing information to potentially large numbers of recipients with differing interests. This advantage is achieved in an embodiment of the invention in which a set of content descriptors for information are associated with a set of multicast addresses by a mapping server, and in which a set of sources and recipients associate themselves with those multicast addresses and their multicast distribution trees, so as to distribute information of interest to recipients broadly without duplication of effort and without excess use of multicast addresses.